Sponges are not the most intimidating of animals. They tend to be blobby, amorphous creatures that spend their lives doing very little other than filtering micro-organisms from the water.
However, the harp sponge Chondrocladia lyra, which inhabits the 3km-deep waters off the Californian coast, is something of an exception – and definitely worthy of a place on our weirdest sea animals list if not our strangest animals in the world list.
Its resemblance to an over-designed toast rack is perhaps appropriate, considering that any invertebrate that happens to stumble into its branches will, indeed, be toast. Those slender appendages are covered in Velcro-like hooks and barbs that snag passing prey, which the sponge then envelops in a membrane and digests using specialised cells.
The branches are not just designed to snare its meals. The spheres at the end of each one are, in fact, bags of sperm, which, when mature, float off in the currents until they become hooked on the barbs of another harp sponge, where they burst open to fertilise its eggs.
The harp sponge was discovered by scientists at Monterey Bay Aquarium Research Institute, using deep-sea robots.
With no gut, or circulatory or nervous system, sponges are among the simplest animals on Earth.
A sponge-like creature is thought to have been the common ancestor of all complex animals.
You can dismantle some sponge species by forcing them through a sieve. The cells then reorganise themselves into a new sponge.